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Versions: (draft-droms-dhc-dhcpv6-rfc868-servers) 00

IPv6 Group                                                      R. Droms
Internet-Draft                                       Cisco Systems, Inc.
Expires: August 24, 2006                                        D. Evans
                                               ARRIS International, Inc.
                                                       February 20, 2006


      Time Protocol Servers and Time Offset Options for IPv6 DHCP
              draft-ietf-dhc-dhcpv6-rfc868-servers-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The Time Protocol Servers option for IPv6 DHCP (RFC 3315) carries the
   IPv6 addresses of servers that a host should use for the Time
   Protocol (RFC 868).  The Time Offset option carries the offset in
   seconds from Coordinated Universal Time (UTC) that a client may use
   to determine its local time.





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1.  Introduction

   The Time Protocol [1] can be used to obtain the current time from a
   server.  The Time Protocol Servers option defined in this document
   provides an option to provide the IPv6 addresses of Time Protocol
   servers to a host through DHCP [2].

   The Time Offset option defined in this document provides an option to
   provide an offset in seconds from UTC that a client can use to
   determine its local time.  This option is only meaningful if the
   server has knowledge of the physical location of the client.

   The options defined in this document are based on the IPv4 DHCP [3]
   Time Server and Time Offset options [4].  This document has no effect
   on IPv4 DHCP, which will continue to use the Time Server option to
   provide the IPv4 addresses of RFC 868 Time Protocol servers and the
   Time Offset option to provide the offset between UTC and local time
   to clients.


2.  Terminology

   The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be
   interpreted as described in RFC2119 [5].

   Throughout this document, unless indicated otherwise for clarity, the
   acronym "DHCP" refers to "Dynamic Host Configuration Protocol for
   IPv6" [2].


3.  Format of the Time Protocol Servers option

   The Time Protocol Servers option defines a list of Time Protocol
   servers available to the DHCP client.  The IPv6 address of each
   server is included in the option.  The addresses SHOULD be listed in
   order of preference.  The addresses MUST be unicast or anycast
   addresses.

   The Time Protocol Servers option has the following format:











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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      OPTION_RFC868_SERVER     |        option-len             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                       server-address1                         |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                       server-address2                         |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       .                                                               .
       .                                                               .
       .                                                               .
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                       server-addressN                         |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code         OPTION_RFC868_SERVERS (TBD).
   option-len          16 * N.
   server-address1-N   The IPv6 addresses of the Time Protocol servers.


4.  Time Offset option

   The Time Offset option specifies the offset in seconds from
   Coordinated Universal Time (UTC) that the client should use to
   determine its local time.  The offset is expressed as a two's
   complement 32-bit integer.  A positive offset indicates a location
   east of the zero meridian and a negative offset indicates a location
   west of the zero meridian.  It is recommended that this option be
   used only when the concept of local time based on a 24-hour day is
   known to be meaningful.

   The Time Offset option has the following format:









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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      OPTION_TIME_OFFSET       |        option-len             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         time_offset                           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code         OPTION_TIME_OFFSET (TBD).
   option-len          4.
   server-address1-N   Offset in seconds from UTC.


5.  Security Considerations

   A server could use this option to return invalid or incorrect
   addresses or valid addresses of malicious Time Protocol servers to
   the client.  A server could use this option to return incorrect or
   inappropriate time offset values to the client.

   Authentication of DHCP messages [2] can be used to ensure that the
   contents of this option are not altered in transit between the DHCP
   server and client.


6.  IANA Considerations

   IANA is requested to assign an option code from the IPv6 DHCP options
   registry to OPTION_RFC868_SERVER and OPTION_TIME_OFFSET.


7.  Normative References

   [1]  Postel, J. and K. Harrenstien, "Time Protocol", STD 26, RFC 868,
        May 1983.

   [2]  Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
        Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
        RFC 3315, July 2003.

   [3]  Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
        March 1997.

   [4]  Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
        Extensions", RFC 2132, March 1997.

   [5]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.



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Authors' Addresses

   Ralph Droms
   Cisco Systems, Inc.
   1414 Massachusetts Avenue
   Boxborough, MA  01719
   USA

   Phone: +1 978.936.1674
   Email: rdroms@cisco.com


   D. R. Evans
   ARRIS International, Inc.
   7912 Fairview Road
   Boulder, CO  80303
   USA

   Phone: +1 303.494.0394
   Email: N7DR@arrisi.com


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Acknowledgment

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   Internet Society.































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